Warm water gives cyanobacteria a competitive advantage. Environmental Protection Agency’s most recent surveys on national water quality, nutrient pollution in the United States is a problem in more than one-third of lakes and about half of all rivers and streams. Most excess nutrients enter waterways via agricultural runoff (particularly from animal manure and chemical fertilizers that get washed from farms by rain), leaked waste from animal feedlots, stormwater runoff from urban and suburban areas, and discharges from wastewater treatment facilities. But when they run off urban and rural surfaces and flow into a river, lake, pond, or reservoir in excess-a phenomenon known as nutrient pollution-they act like fertilizer and promote the growth of algae and bacteria. Nutrients like nitrogen and phosphorus, essential to plant growth, are a natural part of underwater ecosystems. The following are some of the main freshwater algal bloom causes: Nutrient pollution HABs occur both naturally in the environment and as a result of human activities, but the latter are vastly increasing the frequency, prevalence, and toxicity of HABs. While a bloom of golden algae can cause massive fish kills, it hasn’t been shown to pose a health threat to humans. Golden algaeĪlthough found mostly in oceans, golden algae ( Prymnesium parvum) are an emerging problem in freshwater rivers, reservoirs, and lakes, particularly those with higher salinity (due to higher mineral content), such as those found in Texas and New Mexico. The most frequently reported type of bloom-forming cyanobacteria is Microcystis. Some, though not all, types of cyanobacteria can produce dangerous cyanotoxins.

Cyanobacteria are, as the name suggests, bacteria-but they perform photosynthesis, like algae do, and are often referred to as blue-green algae. Cyanobacteria (blue-green algae)Ĭyanobacteria blooms are the most common type of HABs in lakes, ponds, and other freshwater systems in this country, although they can occur in brackish and saltwater environments, too. Most freshwater HABs in the United States are produced by cyanobacteria. The Most Common Types of Freshwater Harmful Algal BloomsĪny type of algae can proliferate into a HAB under the right conditions. A harmful algal bloom, or HAB, is a bloom that produces toxins that are dangerous to humans and potentially other organisms. Not all algal blooms are toxic, but research indicates that a growing number are. Algal blooms can be many colors, including blue-green, yellow, brown, pink, and red. Depending on the type of algae or bacteria that cause it, an algal bloom may produce bad-smelling scum, foam, froth, or a paintlike slick. An algal bloom is the overgrowth of microscopic algae or algae-like bacteria in fresh, salt, or brackish waters. Here’s what you need to know about algal blooms, including their causes and consequences.Ĭritical to aquatic food webs, algae are photosynthetic organisms-in other words, they derive energy for growth from the sun. It’s predicted that climate change will only exacerbate the problem. While they aren’t a new phenomenon (Spanish explorers recorded blooms along Florida’s coast in the 1500s), reports of freshwater harmful algal blooms have increased significantly over the past 40 years, and they are now an environmental problem in all 50 states.

Algal blooms are odious, but more important, they can also be dangerous, imperiling public health and aquatic ecosystems, and costly, affecting local economies. They also form in bodies of fresh water, making lakes, ponds, or your favorite swimming hole smelly and slimy. But harmful algal blooms don’t just affect our oceans. You may have read about algae taking over giant swaths of coastlines, closing beaches and turning the sea a foamy brownish red in a phenomenon known as a red tide. Preventing Freshwater Harmful Algal Blooms.What Are the Effects of Freshwater Harmful Algal Blooms?.What Causes Harmful Freshwater Algal Blooms?.The Most Common Types of Harmful Algal Blooms.

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